Low urinary iodine postpartum is associated with hypothyroid postpartum thyroid dysfunction and predicts long-term...

Area of Science:

• Endocrinology
• Reproductive Health
• Nutritional Science

Background:

• Postpartum thyroid dysfunction (PPTD) presents with hyperthyroid and hypothyroid phases, increasing long-term hypothyroidism risk.
• Iodine status significantly impacts thyroid function, with Western Australia generally considered iodine-replete.
• Understanding iodine's role in PPTD is crucial for predicting long-term thyroid health outcomes.

Purpose of the Study:

• To assess iodine status in women with and without PPTD.
• To investigate the association between postpartum iodine status and the development of long-term hypothyroidism.

Main Methods:

• A case-control study with a 12-year follow-up was conducted.
• 149 women (74 with PPTD, 75 controls) were assessed at 6 months postpartum, with 98 followed up at 12 years.
• Measurements included urinary iodine concentration (UIC) and thyroid function tests.

Main Results:

• Lower urinary iodine concentration (UIC) at 6 months postpartum was significantly associated with hypothyroid PPTD.
• Decreased log UIC and UIC < 50 μg/l were strong predictors of hypothyroid PPTD (ORs 2.54 and 4.22, respectively).
• Low UIC independently predicted hypothyroidism at 12-year follow-up, irrespective of antibody status.

Conclusions:

• Low postpartum urinary iodine concentration is a significant predictor of both hypothyroid PPTD and long-term hypothyroidism.
• The study suggests low iodine may result from more severe thyroiditis, leading to increased long-term hypothyroidism risk.
• Monitoring iodine status postpartum is essential for identifying women at risk of persistent thyroid dysfunction.